Transducer housing for sonic apparatus



March 23, 1954 Filed Feb. 17, 1950 C. W. HARRIS ET AL TRANSDUCER HOUSING FOR SONIC APPARATUS 4 Sheets-Sheet l JaseFh ZZZ-fizzle Lily-2 5 ZZZ-H5551? yflm wa w March 1954 c. w. HARRIS ET AL 72,94

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F/aie 7/7f5k17555 XFHEQUEZ'ZQW 575512257511 5 X mgagysies) m Z 11 Patented Mar. 23, 1954 TRANSDUCER HOUSING FOR SONIC APPARATUS Clyde W. Harris, Socorro, N. Mex, and Joseph M. Kime, Akron, Ohio, assignors to The B. F. Goodrich Company, New York, N. Y., a corporation of New York Application February 17, 1950, Serial No. 144,624

5 Claims.

This invention relates to housings for sound transmitting and receiving apparatus and pertains more particularly to underwater transducer housings which enclose apparatus for determining the bearing and/or range of an object within the transmitting and receiving range of the transducer.

It is an object of this invention to provide a transducer housing which permits substantially all of the sound waves propagated against the walls of the housing to be transmitted through the walls of the housing into the surrounding medium.

It is also an object of this invention to provide an underwater transducer housing which will withstand external pressures normally exerted on the walls of the housing during submergence.

A further object of this invention is to provide an underwater transducer housing which when advanced through the water at speeds at which a ship travels does not cause disturbances in the water which seriously impair the operation of the sonic detecting apparatus.

Other objects of this invention will be apparent from the description and drawings which follow:

The general operation of underwater search apparatus comprises propagating a relatively narrow, conical beam of sound waves into the surrounding medium at frequent intervals and at numerous bearings, and detecting any sound waves reflected from objects foreign to the medium. At each step or interval the operator transmits a pulse of sound waves into the surrounding medium and waits for a return pulse reflected or echoed from an object foreign to the medium. If no sound waves are reflected to a receiving transducer which is located preferably in conjunction with a .transmitting transducer or which may be the same transducer which transmitted the pulse of sound waves, the operator rotates the transmitting and receiving transducers to another bearing and continues to search. If sound waves are reflected from an object, such as a submarine, the reflected sound waves or echo is picked-up by the receiver transducer and the sound waves are transformed into audible and/or visual indications.

The transmitting and receiving transducers must be enclosed within protective housings for underwater use in order to prevent damage to the transducers and to provide a minimum of turbulence in the flow of water around the transducer.v It is essential of course that the walls 2 of the housing be as nearly transparent as possible.

From the point of view of strength and simplicity of construction, the most satisfactory materials for the wall of such a housing would be one of the common structural metals such'as iron, steel, aluminum, or alloys such as bronze, brass, etc. However, conventional housings with walls of such metals and with suificient structural strength have in the past proven unsatisfactory because most of the sound striking such a wall was reflected and only a very small proportion if any was transmitted through it. For this reason it has been necessary to employ for the walls of the housing other materials, such as rubber, which are much more highly transparent to sound, even though they lack the other necessary mechanical properties and so require elaborate and expensive reinforcing structures to compensate for these defects. I y

We have now discovered that housings whose walls are highly transparent to sound may be constructed from common structural metals provided that the wall thickness is uniform and that the angle between the wall and a line from the Wall to the sonic transmitter or receiver is substantially constant and within a certain specific range throughout the extent of the wall area.

In teaching this invention two embodiments of our invention are shown and described, however, it will be understood that the embodiments shown in the appended drawings and described herein are intended merely as illustrations of our invention and are not intended to limit the scope of this invention.

In the drawings: I

Fig. l is a view in elevation partly broken away and in section of an underwater transducer housing embodying our invention together with a supporting member;

Fig. 2 is a section on line 22 of Fig. 1;

Fig. 3 is a section in enlarged scale showing the juncture of the rubber body member of the housing shown in Fig. 1 to the flange on the securing lip of the housing;

Fig. 4 is a section in enlarged scale showing the junctures of the rubber body member and the metal body member of the housing shown in Fig. 1 to a joining band;

Fig. 5 is a plan view of the underwater transducer housing shown in Fig. 1;

Fig. 6 is a view in elevation partly broken away and in section of another embodiment of my invention together with a supporting member;

to sound Fig. 7 is a plan view of the underwater transducer housing shown in Fi 6;

Fig. 8 graphically indicates the variance in transmission of sound waves at various frequen cies through an aluminum plate of a finite thickness as the angle of incidence which the sonic beam forms with the plate is varied; and

Fig. 9 graphically indicates the variance of the angle of incidence at which transmission maxima occur for aluminum and steel plates of finite thickness as the product of plate thickness and frequency is varied.

The underwater transducer housing it as shown in Fig. 1 is comprised of two sections, a metal wall member II and an acoustical rubber wall member I2. Since a transducer housing whose wall member is constructed entirely of metal and of a contour so that the wall surface of the housing forms substantially a constant angle with a line from the transducer does not providea desired-overallcontour, it is preferable that a portion of the housing comprise an acoustical ru-bber wall member to provide a streamlined contour for the housing and to provide sufficient space within said housing to permit transmitting and receiving transducers to be properly mounted therein.

Metal wall member I I, as shown in Figs. 1 and .5,-has a curvature which is nonspherical and streamlined such that the angle of incidence formed by a sonic beam emitted from or received by a transducer (not shown), whose center of emission is situated at position I It, with the curved surface of metal wall member 1 I is substantially constant. .A surface that maintains a constant angle with any radius vector radiating from a point may be constructed by rotating a segment of an equiangular spiral (having said point as a polar center) about a line passing through said point. The constant angle which a radius vector from the transducer forms with metal wall member II will vary in magnitude in transducer housings constructed in accordance with this invention depending upon the thickness of metal wall member II, the particular metal from which metal wall member I I is constructed, and the frequenc of the sound waves.

The metal wall member I I may be constructed of any metal or alloy which has sufficient structural strength when in the desired configuration to withstand the external forces exerted on the housing, such as iron, steel, aluminum, brass, etc. Although any appropriate method may be used to form the metal wall member I I, it is preferable, from a practical standpoint, to cast metal wall member II in a mold in the form of a single unitary element.

A portion of housing I!) is provided with an acoustical rubber wall member h": as shown in Figl to provide a streamline contour for the entire outer surface of housing Iiiand to provide sufiicient space within housing It to properly -mount the transmitting and receiving transducers. The rubber wall member I2 is constructed of conventional acoustical or sound rubber layers I 5, I 5, that is, rubber layers formed from a rubbery composition which transmits substantially all of the sound waves propagated against its surface, and is reinforced with a rigid grating or backing member I6. It is preferable that grating I6 be embedded between and adhered to layers of acoustical rubber, so that the latticework of grating I6 is not exposed to moisture which might weaken the metal because of corrosion. Satisfactory adhesion of the rubbery layers I5, IE to grating It is obtained by vulcanizing the rubbery layers I5, I5 in contact with grating IG. Grating It may be constructed of any rigid reinforcing material, such as iron, steel, aluminum, brass, bronze, etc., which will not be deformed by forces normally exerted on housing Iii.

Rubber wail member i2 is secured to metal wall member H by securing flange E1 on rubber wall member I2 to joining band i8, and securing flange as on metal wall member I i to joining band I8; and rubber wall member I2 is secured along flange 2G to flange 22 on securing lip 23. It is preferable that securing lip 23 and metal wall member E I be a single unitary element to provide maximum structural strength in housing it. The heads of any rivets and/ or bolts projecting from the outer surface of housing H] are preferably removed, so that housing it has a smooth unbroken outer surface which minimizes cavitation or turbulent disturbances in the water caused when housing In is advanced through the water,

A removable plug 24 is provided in the bottom portion of housing it to provide a means for removing water from the interior of housing I0.

Eolting flange 25 of ferrule 25 is bolted to securing lip 23 of housing it, and bolting flange 21 of ferrule 26 is bolted to securing flange 28 of supporting shaft 29.

Conduit 3G extending through supporting shaft is provides a passage for electrical wires, etc. that furnish energy to and receive energy from the sound transmitter and receiver.

in another embodiment of this invention, as shown in Fig. 6, metal wall members 31, 3I are constructed of a rigid metal or alloy, such as iron, steel, brass, aluminum, bronze, etc., and have a curvature which is nonspherical and streamlined, as shown in Figs. 6 and '7, such that a line from the point. of emission 32 of a sonic beam emitted from a transmitting transducer (not shown) to any point on a metal wall member SI, 'I forms a constant angle with a tangent to the curved surface at that point. In this embodiment of this invention the two metal wall members 3!, 3I are identical and may be formed by rotating a segment of an equiangular spiral about any radius vector of said spiral. The curvature of metal wall members 3!, 3! is such that any radius vector originating at point 32 and intersecting a metal wall member 3! will form an angle of 33 with the tangent to the curved surface of the end section 3I at the point of intersection of the radius vector with the surface.

Center section 33 which provides a desired streamline contour to housing 34 without substantially decreasing the transmitting properties or strength of the underwater transducer housing as is constructed of conventional acoustical or sound rubber layers 35, 35 between which is embedded and adhered a reinforcing grating 33. Preferably the rubber layers 35, 35 are vulcanized to grating 35 forming an integral unit.

A removable plug 31 permits water to be drained from the interior of housing 34.

Center section 33 of housing 34 may be secured to metal Wall members 3|, 3| and securing lip 38 in the same manner as used in the embodiment of our invention shown in Fig. 1.

Securing lip 38 on housing 3% provides a means for attaching housing 34 to ferrule 26 which is in turn secured to supporting shaft 29.

To obtain satisfactory transmission of sound waves through the walls of the equiangular metal sections of the transducer housing, the transdueer transmitter and receiver must be placed at a position corresponding to the polar center of construction of the equiangular spiral segment which forms the equiangular contour of the metal sections.

It is desirable that housings for underwater sonic apparatus be completely filled with water during the operation of the apparatus to obtain the optimum transmission of sound Waves through the surrounding media.

If desired, the outer surfaces of the metal wall members may be covered with acoustical rubber to protect; th metal from corrosion and/or to alter the contour of the transducer housing.

As previously mentioned, if a narrow sonic beam'is propagated against a metal plate of uniform thickness, angles of incidence are observed at which transmission maxima occur depending upon the thickness of the plate, the frequency of the sonic waves, and the metal from which the plate is constructed. As shown in Fig. 8, an aluminum plate having a uniform thickness of 0.031 inch transmits all of the sonic waves having a frequency of 500 kilocycle when the sonic beam form an angle of incidence of approximately 57 with the surface of the plate. As the frequency of the sonic waves is increased, the angle of incidence at which maximum transmission occurs, decreases, and when the sonic beam has a frequency of 800 kilocycles a transmission maximum of 92 percent at an angle of incidence of 47 is observed, and at a frequency of 1000 kilocycles a transmission maximum of 81 percent is observed at an angle of incidence of 40. The curves illustrate that the angles of incidence for a desired sound wave frequency at which satisfactory transmission of sound waves through a metal plate occurs falls within a limited range depending upon the metal used to form the plate and the thickness of the metal plate. As the angle Of incidence increases, the percentage of sound waves of a particular frequency transmitted through the metal plate decreases rapidly after the transmission maximum has been reached, and, as a certain angle of incidence is reached, the sound waves are totally reflected from the surface of the plate at which angle of incidence no transmission of the sonic waves through the plate occurs.

Sound waves are propagated in three modes, flexural vibrations, transverse vibrations, and longitudinal vibrations. In general, for each mode of propagation, different angles of incidence are observed at which transmission maxima occur when sound waves strike a metal plate of uniform thickness. It is preferable, however, that the surface curvature of the transducer housing be constructed such that the constant angle of incidence which the sonic beam forms with the surface of the housing be that at which maximum transmission through the metal plate is observed for sound waves propagated by flexural vibrations, since sound waves propagated by transverse and longitudinal vibrations often cause disturbances within the walls of the housing which interfere with the operation of the sonic detecting apparatus.

As shown in Fig. 9, the angles of incidence at which transmission maxima occur decrease with an increase in the product of plate thickness and sound wave frequency. It is obvious that for a particular angle of incidence and a particular metal, if the frequency of the sonic beam is substantially varied the thickness of the metal plate must also be varied, so that the product of plate thickness and frequency remain substantially the same, to obtain satisfactory sonic transmission through the housing.

To design a transducer housing in accordance with this invention, it is preferable that the following procedure be observed. Select the metal from which it is desired to form the metal wall memb'er'or members of the housing and the frequency range within which the sonic detecting apparatus is to operate. Experimentally determine the values of the product of frequency times plate thickness at which transmission maxima occur for that. particular metal due to.

the propagation of sound by flexural vibrations. Select a desired angle of incidence at which a transmission maxima occurs and which, when used as the constant angle in the formation of an equiangular spiral, provides a satisfactory contour to the metal wall members of the housing when a segment of the spiral is rotated about a radius vector of the spiral. Referring to an appropriate graph, such as those shown in Fig. 9, and obtaining the appropriate value of the product of frequency times plate thickness, the required wall thickness for the metal section of the housing is readily determined by division of the maximum frequency of sonic transmission desired to be used into the product of frequency times thickness obtained from the graph.

It is obvious that transducer housings of numerous configurations may be constructed by merely choosing a difierent angle of incidence from which the equiangular spiral is constructed which determines the curvature of the metal section or sections of the transducer housing.

A transducer housing constructed in accordance with this invention has excellent properties for transmitting sonic waves of a desired frequency propagated against its surface, increasing the efiiciency of the underwater detecting apparatus as compared to detecting apparatus genclosedin housings of conventional construcion.

Equiangular metal wall members in a, transducer housing constructed in accordance with our invention provide greater strength for the housing rendering the housing structurally stronger than housings of conventional construction having their walls constructed entirely of reinforced acoustical rubber,

It is clear that obvious variations and modifications may be made Without departing from the spirit and scope of this invention as defined in the appended claims.

We claim:

1. An underwater-transducer housing which comprises a streamlined hollow rigid self-supporting sound-transmitting metal body member, said metal body member having a uniform wall thickness and having a curved surface conforming substantially in contour to a surface generated by the rotation of a segment of an equiangular spiral, that intersects all radii vector thereof at an angle substantially the same as an angle of incidence at which maximum transmission of sound waves propagated by flexural vibrations through a metal plate of the same metal as said metal body member and having the same wall thickness as said metal body member occurs, about a radius vector of said spiral.

2. An underwater-transducer housing which comprises a streamlined hollow rigid self-supporting sound-transmitting metal body member, said metal body member having a uniform wall thickness and having a curved surface conforming substantially in contour to a surface gener- I-byz'th'e rotation of :assegment :of anequiangular spiral, that intersects tall radii "vector thereof atran angle isubstantiallyzthe same as an angle f :incidence at which :maximum transmission of sound waves propagated by flexural .tvibraticns through a metal plate "of the same metal as said :metal body member :and having 'the'same wall thickness'as said metal body member occurs, about a radius vector of saidspiral, 'and 'a reinforced sound-transmitting acoustical rubber wall member.

3. AP. underwatentransducer housing which comprises a streamlined hollow rigid self-supportingsound transmitting metal body member, saidrme'talbOdy member having a uniform wall thickness and having a curved surface conf0rm ing substantially in contour to a surface generatediby the rotation of a segment of an equiangular spiral, that intersects all radii vector thereof atan angle substantially the same "as an angle of incidence at which maximum transmission of sound waves propagated by fiexural vibrations through a metal plate of the same metal as said "metal body member and having theisame Wall thickness as said metal body mem- :ber occurs, about a radius vector of said spiral, and anacoustical rubber wall member reinforced with a rigid material having a plurality of interstice'sitherein.

4. An underwater-transducer housing which comprises a streamlined hollow open-ended rigid self-supporting sound-transmitting metal body member, :said metal body'member having a uniform wall thickness and having a curved surface conforming substantially in contour to a surface :generatedby the rotation of a segment of an equiangular spiral, that intersects all radii vector thereof at an angle substantially the same as an angle of incidence at which maximum trans- :mission of sound Waves propagated by flexural -vibrations through a metal plate of the same metal as said metal body member and having the same wall thickness as said metal body mem- 'ber occursyabout :a radius vectorcf said:splral,

anda hollow'reinforced open-ended soundatransmi-tting acoustical :rubber body -member secured to said metal body member along their margins to forma'hollow unit.

55. An 'underwater transducer housing which comprises a streamlined hollow open-ended rigid self-supporting sound-transmitting metal body member, said metal body member having a uniform wall thickness and having a curved surface conformingsubstantially in contour to asurface generated by the rotation of a segment of an equiangular spiral, that intersects all radii'vector thereof at an angle substantially the same as'an angle of incidence at which maximum "transmission of sound waves propagated by fiexural vibrations through'a 'metal plate of the "same :Reierences Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,403,990 Mason July .16, 1946 2,407,643 Batchelder Sept. 17, 1946 2,407,697 Williams Sept. 1'7, 1946 2,417,830 Keller Mar. 25, 1947 2,444,911 Benioff July 13, 1948 2,452,068 Peterson Oct. 26, 1948 2,460,274 Benioff Feb..1, 1949 2,472,107 Hayes et al. June '7, 1949 2,519,360 .Dow Aug.'22, 1950 2,575,339 Fitzgerald Nov. 20, 1951 

